The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Hyper-secretion from disease-specific cell types is characteristic of many endocrine, immune, and secretory diseases. For example, mast cell secretion underpins anaphylaxis, allergic, autoimmune, and other inflammatory diseases while mucin secretion from epithelial cells contributes to cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Reducing secretion by targeting the core machinery required for secretion can provide a new and effective treatment modality for such diseases. Secretion from such disease-specific cell types is mediated by SNARE proteins, a family of membrane associated proteins that form complexes which mediate vesicle fusion with the plasma membrane and subsequent release of vesicle contents.
Non-neuronal SNAREs are essential for endocrine and metabolic pathways that regulate release of hormones, growth factors, and other signaling molecules. Dysfunction in such secretion pathways results in disease. The non-neuronal SNARE protein SNAP-23, for example, is essential for secretion in multiple disease pathways, including IL-6 and TNF release in arthritis, mucin hypersecretion in COPD, CF, and idiopathic bronchiectasis, platelet secretion in blood hemostasis, insulin secretion in diabetes, renin release in blood pressure regulation, and matrix-degrading enzyme release in tumor cell invasion. Similarly the non-neuronal SNARE protein SNAP-29 is thought to be a negative modulator of neurotransmitter release and a key component in intracellular protein trafficking pathways, with mutations to SNAP-29 resulting in the neurocutaneous syndrome termed CEDNIK.
Blocking secretion by modulating the activity of SNARE proteins has been demonstrated by blocking release of neurotransmitters from motor neurons, using botulinum neurotoxins (BoNTs) to degrade neuronal SNARE proteins that mediate neurotransmitter release. Botulinum neurotoxins (BoNTs), a family of zinc endopeptidases produced by the bacteria Clostridium botulinum, are a powerful class of drugs that are FDA-approved for a wide range of therapeutic and cosmetic applications. There are seven widely recognized BoNT serotypes (BoNT/A through G) and a recently reported serotype H. BoNTs cleave one or more soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins found in motor neurons, blocking neurotransmitter release and leading to flaccid paralysis.
Although among the deadliest natural substances known, BoNTs are widely used in various pharmaceutical and cosmetic applications including cervical dystonia, hyperhidrosis, strabismus, blepharospasm, glabellar lines, and chronic migraine. During intoxication, BoNTs selectively bind to and enter motor neurons via the H chain portion of the molecule. Upon entry into the motor neuron the L chain portion of the molecule is released and degrades the targeted SNARE protein required for controlled neurotransmitter secretion in a highly sequence-specific manner. This results in specific and long-term reduction in the contraction of muscles associated with treated motor neuron. Both binding to motor neurons and degradation of SNAREs utilized in neurotransmitter release are highly specific. For example, BoNT/A, the basis of most BoNT-based pharmaceuticals, blocks secretion from exposed motor neurons by specifically cleaving the protein SNAP-25 but does not bind to other cell types or cleave other SNAP-25 isoforms (such as those expressed in non-neuronal cells). BoNTs have previously been retargeted to non-neuronal cell types through H chain modification. However, therapeutic utility of re-targeted BoNTs is limited by proteolytic specificity for neuronal SNARE proteins. Thus, the therapeutic use of BoNTs are currently limited to neuron-related diseases/conditions and is ineffective for treating non-neuronal secretion disorders.
Thus, there remains a need for BoNTs and/or modified BONTs that exhibit therapeutic secretory inhibition effects in non-neuronal cells.